Drip irrigation systems usually include a continuous irrigation water supply line with separate emitter units installed on the line or in the line, usually at regular intervals. Irrigation water flows through the supply line under pressure and a small amount of water continuously drips out at the intervals where the drip emitter units are installed. Drip irrigation has proved highly successful in producing greater growth of vegetation with the same amount of water when compared with conventional irrigation techniques.
A common and successful approach for controlling drip flow involves use of separate emitter units installed in or on the supply line. The emitter unit taps off a portion of water flowing in the supply line and passes the water through a labyrinth or other circuitous path that produces a large pressure drop in the water and discharges it at a uniform drip rate. Generally, such pressure reducing labyrinthine emitters are successful because they can use a large enough hole in the supply pipe and a wide enough passage through the labyrinth to avoid clogging in most cases and they can be used at higher line pressures.
Because of life forms in the water flowing through the supply line or drainage line, especially in waste water systems, such as septic tanks or reclaimed water irrigation, slime forms along the inside walls of the tube. As the slime grows, the inner wall loses its smooth surface. Laminar flow within the tube is obstructed by the irregular surface, thereby causing a pressure drop within the tube.
In drip irrigation systems, the growth of the slime also occurs within the emitter unit. Slime grows along the path of the labyrinth and across the hole. As the slime grows within the emitter, the flow of water is reduced or shut off.
To solve the slime problem, several supply lines have been developed containing bactericide for killing the slime-forming bacteria. However, the use of bactericides has several problems.
First, most bactericides are toxic to humans and animals and their usage is governed by the Environmental Protection Agency (EPA). Regulations limit the amount of bactericide that can be placed in the supply line. These regulations limit the toxicity of the bactericide in the pipe thereby limiting the amount of control over the bacteria levels in the pipe.
Second, in present systems people who manufacture, sell, or install the drip irrigation system come in physical contact with the bactericide that is on the surface of the supply lines. The toxicity of the bactericide may cause health problems to those handling the supply lines.
Third, the bactericide in the tube is in contact with the soil thereby releasing it into the soil. The bactericide released into the soil kills useful soil bacteria that consume the sewage bacteria which is emitted by the drip line.
There is a need for an irrigation water supply line having the advantages of those containing a bactericide, while also maintaining low manufacturing costs, having the capability of reducing the amount of bactericide released into the soil, and minimizing contact of persons handling the supply line.